This invention relates to a manifold for a plurality of liquid filtration segments wherein filtration is effected by tangential flow of the liquid across a filter surface. More particularly, this invention relates to a manifold which permits stacking of a plurality of filtration segments wherein liquid is introduced and removed from the filtration module while eliminating the need for conduits for connecting the filtration segments.
Prior to the present invention, liquids, primarily aqueous liquids have been filtered by tangential flow segments wherein a plurality of filters are stacked between two manifolds, one at the bottom of the stack and one at the top of the stack. The filtration module stack comprises a collection of one or more filtration modules and associated intermodule gaskets. The filters are separated by appropriate screens and liquid impervious layers to permit liquid flow, as well as filtrate and retentate flow into and from the stack. In addition, flow holes are provided through the layers within the stack. The holes are sealed appropriately to prevent admixture of filtrate with incoming liquid or retentate. The manifold s in each segment are designed so that filtrate is removed from both the top and bottom manifolds while incoming liquid is introduced into one manifold and retentate is removed from the second manifold. This manifold arrangement necessitates fittings to both manifold s in order to supply and remove liquid to and from the stacks. This is undesirable since additional manipulative steps for removing and connecting the fittings are required when it is desirable to replace the filtration elements forming the stack. In addition, the use of two manifolds to remove filtrate from the stack undesirably increases the filtrate volume retained within the stack. Furthermore, the requirement of two manifolds is undesirably expensive.
It has been proposed in U.S. Pat. No. 4,849,102 to provide a manifold for a plurality of filtration segments. However, this manifold arrangement is limited since only two filtration segments can be accommodated while avoiding the need for conduits external the manifold . That is, when more than two filtration segments are utilized, external connecting conduits are required.
Accordingly, it would be desirable to provide a manifold or a plurality of tangential flow filtration segments which utilizes only one manifold and which accommodates any number of a plurality of filtration segments without the need for conduits external of the manifold . Such an arrangement would greatly reduce the number of sealed fittings and would reduce the required apparatus volume for processing a given volume of liquid.